Normal blood comprises a great number of cells, including oxygen-carrying red blood cells and infection-fighting white blood cells. White blood cells include neutrophils, eosinophils and basophils. White blood cells are produced by the hematopoiesis of bone marrow. Normal blood further comprises platelets. Platelets are tiny cell fragments which induce blood coagulation. Blood cells in human body are produced by the hematopoietic system. The hematopoietic system in human body is comprised of a small amount of bone marrow hematopoietic stem cells and different series of hematopoietic cells at different development stages, and is very sensitive to hazardous factors produced by various physical-chemical processes and in vivo metabolism, such as body fatigue, exposure to radiation or certain chemotherapeutic drugs, etc., which may cause diseases such as hematocytopenia induced anemia, bone marrow suppression, etc. In addition, there is also primary hematocytopenia, such as primary thrombocytopenic purpura, etc.
Cancer patients have to receive treatments mainly involving radiotherapy and chemotherapy over a relatively long period of time. Radiotherapy and chemotherapy are therapies in which radiation and cytotoxic agents are used to treat cancers. However, radiotherapy and most of chemotherapy are non-specific, and are toxic to normal and rapidly-dividing cells. High-dose radiation is also toxic to normal and rapidly-dividing cells. This often results in various side effects in patients receiving chemotherapy and radiotherapy. While other normal tissues may also be adversely affected, bone marrow is particularly sensitive to such proliferation-specific treatments as chemotherapy or radiotherapy. Bone marrow suppression, i.e. reduction in the production of blood cells in bone marrow, is one of such side effects. This is reflected by reduction in the proliferation function of the bone marrow, reduction in blood cell count, reduction in peripheral blood leukocytes, reduction in neutrophils, and/or thrombocytopenia, or even aplastic anemia, which severely affects the survival quality of patients or is even life-threatening.
Clinically, patients receiving radiotherapy or chemotherapy are highly susceptible to damages and suffer different degrees of bone marrow suppression. This is reflected by reduction in the number of peripheral blood leukocytes, reduction in the number of neutrophils and/or thrombocytopenia. In the peripheral blood of human body, neutrophils represent about 50-70% of the total number of white blood cells, and the increase and decrease thereof directly affect the change in the total number of white blood cells. That is, white blood cells increase with the increase of neutrophils; and the total number of white blood cells reduces with the reduction of neutrophils. The correlation between the two numbers also represents in the consistency in their significances, i.e. the significance of the increase and decrease of neutrophils is substantially same as that of the increase and decrease of the total number of white blood cells. Patients at bone marrow suppression state are susceptible to infections. Deficiencies in neutrophils and platelets are main reasons for the morbidity and mortality after cancer treatment and result in high cost in cancer treatment.
However, radiotherapy and chemotherapy are currently still the most commonly used means in the treatment of tumors. Complications such as bone marrow hematopoietic suppression and the like induced by radiotherapy and chemotherapy have become important factors affecting the survival quality of patients. Some chemical drugs having explicit efficacy in assisting tumor treatment would cause many adverse effects after use by themselves, which would add the pain of patients. Many medical practitioners are making efforts to seek drugs which are effective and show fewer side effects to combat the damages caused by radiotherapy and chemotherapy.
In current clinical treatment of bone marrow suppression, a variety of growth factors are usually administered to increase the proliferation of hematopoietic cells. Gene recombined hematopoietic growth factors which are marketed in recent years, such as leucomax (rhGM-GSF), filgrastim (rhG-CSF), and the like, are significant when used to increase white blood cells. However, they are expensive and not affordable for most patients. In addition, rhGM-GSF and rhG-CSF neither can be used simultaneously with chemotherapy, nor can be used prophylactically, and only can be administered when leukocytopenia occurs; otherwise toxic side effects would be generated. In addition, gene therapies using hematopoietic growth factors, such as IL-6, IL-3, etc., are still in the stage of animal tests. On the other hand, autologous bone marrow transplant is often used in combination with high-dose chemotherapy, and is difficult to be repeatedly applied. Therefore, finding a safe, effective and inexpensive method to prevent and treat hematocytopenia, in particular that resulted from the side effects of chemotherapy and radiotherapy, and increase the number of white blood cells after chemotherapy and radiotherapy would be very significant for improving the efficacy of chemotherapy and radiotherapy of tumors, prolonging the surviving time and improving the surviving quality of cancer patients.
Thrombocytopenia is a disease in which the reduction of platelets in the peripheral blood causes bleeding of skin mucosa and internal organs, which is mainly manifested by spontaneous skin petechiae and ecchymosis, mucosal bleeding, epistaxis and gum bleeding, occurrence of purple blisters in oral mucosa and tongue, etc. It is a clinically common disease characterized by coagulation disorders and bleeding or more severely hemorrhoea and life-threatening, and represents about 30% of clinical hemorrhagic diseases.
The causes for thrombocytopenia may be divided into: (1) Reduction in production or inefficiency and death of platelets: including inherited and acquired ones. Acquired reduction in platelet production is due to certain factors, such as drug, malignant tumor, infection, ionizing radiation, etc., which damage hematopoietic stem cells or interfere with their proliferation in the bone marrow. It may affect various hematopoietic cell systems, and is commonly accompanying with different degrees of anemia, leukopenia, and significant reduction in bone marrow megakaryocytes. (2) Excessive destruction of platelets: including congenital and acquired ones. Acquired excessive destruction of platelets includes immune and non-immune ones. Common immune excessive destruction of platelets includes idiopathic thrombocytopenic purpura and drug-induced thrombocytopenia. Non-immune excessive destruction of platelets includes infections, disseminated intravascular coagulation, thrombotic thrombocytopenic purpura, etc. (3) Excessive retention of platelets in spleen: the most common example is spleen hyperfunction.
The nosogenesis of thrombocytopenia includes the followings: 1) Immune factors: clinically including thrombocytopenia induced by immune diseases such as severe liver disease, lupus erythematosus, idiopathic thrombocytopenic purpura, etc., in which antibodies damage the platelets; 2) Infectious factors: the common factors causing thrombocytopenia, bacterial and viral infections can directly damage hematopoietic cells, and reduce platelet growth. Acute attack stage of aplastic anemia, acute leukemia, or the like, is often accompanied by severe infection and tendency of bleeding, such as petechiae or erythema on the skin, or nasal bleeding with unknown cause, etc; 3) Drug-related factors: certain drugs may cause the reduction in the platelet count in the peripheral blood, which results in hemorrhagic diseases; and 4) Platelet dysfunction: such as thrombasthenia, Bernard-Soulier syndrome, etc.
Clinically most common thrombocytopenia includes immune thrombocytopenic purpura (ITP) and thrombotic thrombocytopenic purpura (TTP), in which ITP is clinically the most common cause of thrombocytopenia. ITP has long been considered as a hemorrhagic disease caused by thrombocytopenia with unknown causes, and therefore referred to as primary or idiopathic thrombocytopenic purpura. It was later discovered that there are autoantibodies in ITP patients, which identify platelet autoantigens. The binding of autoantibody with platelet antigen shortens the life span of platelets, increases the damage and reduces the number of platelets, indicating that this disease is a hemorrhagic disease associated with immune response.
In clinic, immune thrombocytopenic purpura (ITP) is a relatively common hemorrhagic disease, and may occur at any age stage with an estimated ITP incidence rate of population being 1/10000. It is usually acute in children, and chronic in adults, and usually occurs in children and young adults. The clinical manifestations thereof include skin petechiae and ecchymosis, bleeding in skin mucous, while critically ill patients may suffer from joint pain or abdominal pain, hemafecia, hematemesis, collapse, or the like. More severely, it may develop into purpura nephritis. Primary thrombocytopenic purpura is an immune syndrome and a common hemorrhagic disease, characterized by the presence of anti-platelet antibodies in the blood circulation, which destruct the platelets excessively and cause purpura; and by normal or increased megakaryocytes in bone marrow, and immaturation.
To date, the first choice in treating thrombocytopenic purpura by western medicine is adrenal cortex hormone. Although hormone can increase platelets, but once the hormone is administered at a reduced dose or is discontinued, platelets would reduce again. Frequent use of the hormone would lead significant side effects to human body, and would result in diseases such as central obesity, hypertension and diabetes during the treatment. Other treatments, such as infusion of platelets, spleen resection, and the like, have disadvantages such as increased infection rates, causing active peptic ulcer, bleeding, reduced immune function, hyperglycosemia, or the like, worsened symptoms after drug discontinuance, and non-persistent efficacy. When conventional therapies such as immunosuppressants and spleen resection are employed, the disease cannot be eradicated in many patients due to hormone withdrawal syndrome as a result of the contraindication and side effects of hormones. In addition, immunosuppressants cannot be widely used due to significant toxic side effects, relapse after drug discontinuance, and risks of bone marrow suppression and induced tumors. In recent years, new therapies such as high-dose gamma globulin impact and plasma replacement keep emerging, but there still lacks fundamental therapeutic measures.
Epimedium refers to dry stems and leaves of the plant, Epimedium brevicornum Maxim., Epimedium sagittatum Maxim., Epimedium pubescens Maxim., or Epimedium koreanum Nakai, in the family Berberidaceae and is mainly used in clinic for treating deficiency of kidney yang, impotence and frequent urination, sterility; arthralgia due to wind-dampness, numbness and spasm of limbs, flaccidity of tendons and bones, gait difficulty; deficiency of kidney yang, dyspnea with coughing and shortness of breath. Icariin can increase cardio-cerebrovascular blood flow, promote hematopoietic function, immunological function and bone metabolism, and have efficacies such as tonifying the kidney to strengthen yang, anti-aging, anti-tumor, etc. Icaritin (IT) is a poly-hydroxy flavonoid monomer component in the plant, epimedium, in the genus Epimedium of the family Berberidaceae. Pharmacological studies have shown that IT has a stronger anti-osteoporosis effect than other flavonoid glycoside compounds in epimedium, and has an effect of promoting the activity of osteoblasts and inhibiting the activity of osteoclasts.
In recent years, icariin and icaritin, as important active components in epimedium, have drawn more and more interests from medical practitioners. For example, Chinese patent application CN101637467A discloses use of icaritin in preparing a medicament for the treatment of osteoporosis. U.S. Pat. No. 6,399,579 discloses use of icaritin in the treatment of sexual dysfunction. In “30 Cases of Combined Treatment of Traditional Chinese Medicine and Western Medicine of Chronic Idiopathic Thrombocytopenic Purpura” (published in “Jilin Journal of Traditional Chinese Medicine”, 2010, Issue No. 7), Ningxia Qiang achieved relatively good therapeutic effects in the treatment of chronic idiopathic thrombocytopenic purpura by taking traditional Chinese medicine for invigorating the spleen and tonifying the kidney (Ginseng, Radix Astragali, Chinese Angelica, Fructus Corni, Epimedium, Fructus Psoraleae, etc.) on the basis of western medicine treatment. However, the medicine contains various active ingredients, and has complex mechanism of action. Therefore, it is necessary to conduct more detained studies on the mechanism and the efficacy. In “Studies on Effect of Icariin in Synergistically Inducing IL-2, 3 and 6” (published in “Chinese Journal of Immunology”, 1996, Issue No. 1), Yong Zhao, etc. tested the effect of icariin in synergistically inducing IL-2, IL-3 and IL-6, respectively, by using dependent cell strain method, and the results showed that icariin, with PHA, can synergistically induce mononuclear cell of tonsil to produce IL-2, 3 and 6 in a dose-dependent manner, which suggested that icariin is an effective biological response modifier.
To date, there has been no report in the literature that icaritin has an activity in preventing or treating hematocytopenia, especially immune thrombocytopenia, or radiation- or chemical-induced bone marrow suppression.